There have been known fiber application machines, so-called fiber placement machines, for applying on a male or female mold a wide band formed by several flat ribbon-type fibers, impregnated with a resin, particularly carbon fibers impregnated with a thermosetting or thermoplastic resin. These machines, such as described in patent document WO2006/092514, typically comprise a fiber application head, capable of applying on a mold application surface a band formed of several flat fibers, and a moving system for moving said fiber application head.
The fiber application head, also called a fiber placement head, typically comprises a compacting roller intended to come in contact with the mold along a contact line for applying the band of fibers, and fiber guiding means for guiding fibers in the form of a band on said compacting roller.
The moving system ensures the movement of the application head along at least three directions perpendicular to each other. The moving system may be formed by a standard six-axis robot-type polyarticulated arm, placed on the ground or mounted on a linear axis, with an end wrist joint to which the application head is fixed, or by a portal-frame type cartesian-coordinate robot equipped with an end wrist joint carrying the application head.
During the application or the deposit of the fibers by the compacting roller, the latter maintains a continuous pressure on the application surface of the mold to progressively evacuate the air trapped between the deposited bands of fibers. Following the application of several layers of superposed bands, the resulting part is vacuum-hardened by passing through an oven, generally a autoclave oven.
This compacting operation during the deposit makes it possible to obtain a part before the hardening operation, the dimensions of which substantially correspond to those of the final part obtained after hardening.
In the case of the application of the band formed of a large number of fibers, for example, of eight fibers, application machines and programming software for fiber placement currently proposed do not make it possible to deposit a band of fibers on edges or convex surfaces with a low radius of curvature, for example less than 10 mm, while compacting all the band fibers, and with orientations of about 45° or 135° with respect to the edge or the generatrix line of the convex surface.
In the absence of compacting, the evacuation of air bubbles is only carried out during the vacuum hardening, and the final part thus exhibits folds of surplus material at said edges or convex surfaces.
To date, these different parts with edges and/or convex surfaces are obtained by producing plane parts by means of an application machine of the aforementioned type, then by a folding and/or bending operation of the plane parts before hardening. Apart from the fact that this folding or bending step requires an additional complex operation, it also leads to the formation of folds at the internal layers, which affects the resistance properties of the final part.
As a result, the application machines proposed to date are not used for essential parts, particularly in the aeronautics sector, such as the spars of an airplane wing, beams of wind turbine blades, aerodynamic profiles, so called L-shaped fittings or reinforcements.